Tratto dall'help di ACB:

"TRAINABLE CHANNEL" - compression of another portion of information taking into account all earlier compressed information -context. For example: you transmit by modem a corrected version of the text transmitted yesterday. In this case it's possible to expect 100-time compression, in other words, only the latest information was transmitted. Besides, there's a possibility to maximize compression of the data of a certain type. For example, create a context from the files *.txt and use this txt-context to compress txt-files. In addition, such an approach ensures additional data protection against non-authorised access -it's impossible in principle without knowledge of the whole background data being decoded. In unpacking the context should be the same as in packing. The context file is renewed each time it is used. For example: you packed the text of an agreement using the context, the context file was renewed and can't
be used to unpack the received archive but the receiving party (in our example "office") has a yesterday's context identical to yours up to the latest packing, that is why the transmitted archive in the office will be unpacked and the context file will be renewed and identical to yours. If you want to ban renewal of the context file set it in Read_Only.